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Aquatic Species Program (ASP): Lessons Learned
AFOSR WorkshopWashington, D.C.February 19-21, 2008Sponsored byAir Force Office of Science
Eric E. Jarvis, Ph.D.National Renewable Energy LaboratoryNational Bioenergy [email protected] NREL/PR-510-43232
The ASP Didn’t Invent the Concept of Fuels from Algae… Algae for methane (via anaerobic digestion)
• Meier (1955); UC Berkeley 1957-59 (Oswald and Golueke)
• Wastewater use, recycling of CO2 and nutrients
Revival during Energy Crisis of 1970’s• Uziel et al. (1975); Benemann et al. (1976-80)• Still focused on methane and hydrogen• Energy Research and Development Administration
(ERDA)• Later DOE (SERI founded in 1977)
…But the ASP Took the Concept to the Next Level
Supported work at SERI/NREL and through dozens of subcontracts to universities and private companies
Focus turned to lipid oils, diesel replacements, microalgae rather than other “aquatic species”• Algal hydrogen research moved to different program
Explored all aspects of the technology
The ASP Funding Rollercoaster
ASP began in 1978
Ended in 1996 to focus lean budgets on bioethanol
Overall investment ~$25M
The ASP Chronology
Program Justification
Lignocellulosic ethanol can’t for substitute for energy-dense diesel (and aviation) fuels
FAME (biodiesel) was evolving as an option• Renewable oil sources insufficient to meet diesel
fuel demand• Algae offers alternative
Energy security concerns dominated at first, later global climate change became important factor (flue gas CO2 capture)
ASP Topic Areas
1. Microalgae collection and screening2. Physiology, biochemistry, and genetic
engineering3. Process engineering4. Outdoor mass culture5. Analysis
Microalgae Collection and Screening
>3000 strains of microalgae collected over 7 years Western,
northwestern, southeastern US and Hawaii Most from
shallow, inland saline habitats
Microalgae Collection and Screening…
Screened for tolerance to salinity, pH, temperatureScreened for neutral
lipid production (Nile Red)Media optimization
• SERI Type I and II, etc.
• Laboratory surrogates
Microalgae Collection and Screening… Collection narrowed to 300 most promising
strains (partly by attrition) Primarily greens (Chlorophyceae) and diatoms
(Bacillariophyceae)Amphora, Chaetoceros, Chlorella, Cyclotella,
Monoraphidium, Nannochloris, Nannochloropsis, Navicula, Nitzschia, Phaeodactylum, Tetraselmis, Thalassiosira
Some made axenic In 1996, remaining cultures transferred to the
Center for Marine Microbial Ecology and Diversity (CMMED) at U. Hawaii About half the strains still available
Microalgae Collection and Screening:Lessons Learned
• Many microalgae can accumulate neutral lipids
• Diatoms and greens most promising
• No perfect strain for all climates, water types
• Serial transfer less than ideal
Physiology, Biochemistry, and Genetic Engineering
• Studies on induction of lipid accumulation response–N or Si depletion
• What are the biochemical and genetic underpinnings of photosynthate partitioning?– The “lipid trigger”
Physiology, Biochemistry, and Genetic Engineering…• Cyclotella cryptica primary model organism for biochemistry
• Identification of key enzymes in fatty acid and carbohydrate (chrysolaminarin) pathways
–Acetyl CoA carboxylase(ACCase) activity increases upon Si depletion (Roessler 1988), enzyme characterized
–UDP glucose pyrophosphorylase (UGPase) and chrysolaminarin synthase activities also charac-terized (Roessler 1987, 1988)
Physiology, Biochemistry, and Genetic Engineering…
Genetic “toolbox” developed• Transient and stable marker systems• Effective methods of DNA introduction• Achieved genetic transformation of
diatoms C. cryptica and Navicula saprophila (Dunahay et al., 1995)– Antibiotic resistance marker under control of
ACCase gene promoter & terminator– Cell wall penetration via “biolistics”– Random chromosomal integration
Physiology, Biochemistry, and Genetic Engineering…
Key genes isolated from C. cryptica• ACCase gene cloned (Roessler and Ohlrogge, 1993)
– First from photosynthetic organism• UGPase gene cloned (Jarvis and Roessler, 1999)
– Chimera with phosphoglucomutase (previous step in pathway)
Attempts at gene modulation• Successful ACCase overexpression (2-3x)• Successful UGPase overexpression, but not turn-
down• No effects seen on lipid accumulation in these early
experiments
Physiology, Biochemistry, and Genetic Engineering: Lessons Learned
• Choosing right starting species is critical
• Lipid induction upon nutrient stress doesn’t help productivity
• Key enzymes change activity upon induction, but no obvious “lipid trigger”
• We have only begun to scratch the surface–Need to understand pathways, regulation, devise
genetic strategies
Process Engineering
• Explored methodologies for dewateringalgal suspensions and solvent extraction of oil
• Tested transesterification of lipids to fuel (no other methods, scale-up, fuel characterization, or engine testing of algal fuels)
• Laboratory-scale experimentation, but not major focus of project
Process Engineering: Lessons Learned
• The scale, energy input, and cost challenges make dewatering and extraction significant hurdles
• Flocculation/bioflocculation may be most promising route for dewatering
• Solvent extraction of oil through the cell wall is feasible
• Transesterification is straightforward, but many challenges in making a quality fuel
• There’s much more work to be done!
Outdoor Mass Culture
Hawaii experiments (1980-87)• Patented “Algae Raceway Production
System” (ARPS)• 60 cm deep, 48 m2raceway with cover
California experiments (1981-86)• “High Rate Pond” (HRP) system (developed at UC Berkeley)• Four 200 m2, three 100 m2 open raceways, paddlewheel mixed• 15-30 cm deep• Many species tested, Amphora and Cyclotella did well
Israeli experiments (1984-86)• Multiple investigators, configurations, species, harvesting
methods
Outdoor Mass Culture…
Roswell, NM facility (late 1980’s)• Subcontract to Microbial
Products, Inc. (Weissman et al., 1989)
• Based on the HRP design• Two 1,000 m2 raceway ponds,
15-25 cm deep• Cyclotella, Monoraphidium,
Amphora, Tetraselmis, etc.
Outdoor Mass Culture: Lessons Learned
• Important successes–Typical productivities 15-25 g/m2/day biomass over
productive months
–Roswell gave occasional productivities approaching 50 g/m2/day (but closer to 10 g/m2/day overall)
–NOTE: But not 50% lipid!
–Long-term, stable cultivation achieved
–CO2 utilization >90% with proper sump and pH control
–Mixing energy low in paddlewheel systems
Outdoor Mass Culture: Lessons Learned…
• Issues identified–Temperature affects productivity, culture collapse,
invasion, grazers, nighttime respiration, O2 inhibition–Invasion by native microalgae species–Lab conditions ≠ outdoor culture conditions–Productivity ≠ persistence–O2 levels problematic–Hydraulics critical–Water loss (evaporation and percolation)–Low lipid contents
Analysis
Resource assessments• Land suitability
– Insolation– Slope– Land use– etc.
• Water (saline aquifers)
• CO2 sources• Focus on US desert
southwest
Analysis…
Life Cycle Analysis (LCA)
• Small amount of LCA done
• Focus on co-combustion of algae
• Needs to be revisited
Analysis…Technoeconomics• Several different analyses over the course of the
program (Benemann and others)
• Many assumptions and unknowns, differing conclusions
• Most optimistic of analyses not competitive with 1996 petroleum costs–Most recent analysis (Kadam 1995) estimated cost of
unextracted lipid from $186/bbl (“current” case) to $59/bbl (optimistic “improved” case) with no CO2 credit
–Petroleum at <$20/bbl in 1996 and “DOE expects petroleum costs to remain relatively flat over the next 20 years.”
Analysis: Lessons Learned• Ample land, water, CO2 resources available in
Southwest for “several Quads” (30+ billion gallons?) of fuel per year
• Economics are challenging– Biological productivity largest influence on fuel cost– Capital costs huge factor– Unlined, open ponds only option– Land costs minor– CO2 cost and transport distance significant– Need to get value from residual biomass– Water, nutrient recycle
• Significant R&D still required to reduce costs!
What’s Changed Since 1996? Oil prices didn’t stay flat
Increasing concern about CO2
New photobioreactor designs, advances in material science
Explosion in biotechnology• Advances in metabolic
engineering• Genomics, proteomics,
metabolomics, bioinformatics, etc.
DOE Joint Genome Institute
Accessing the Legacy of the ASP Close-out report (Sheehan, et al. 1998)
• http://govdocs.aquake.org/cgi/reprint/2004/915/9150010.pdf
Electronic documents• Ongoing effort at NREL to scan
old ASP reports and make publicly available
• >100 electronic documents now posted on the NREL Publications website– http://www.nrel.gov/publications/– Search “microalgae”
Conclusions
The ASP has provided a solid foundation for fuels-from-algae research
Sheehan et al. presaged the current revival in this field:
… this report should be seen not as an ending, but as a beginning. When the time is right, we fully expect to see renewed interest in algae as a source of fuels and other chemicals. The highlights presented here should serve as a foundation for these future efforts.